Carbon is an important element in the formation of industrial steel. The properties and metallographic structure of steel depend to a large extent on the content and distribution of carbon in the steel. The influence of carbon in stainless steel is very obvious. .

The effect of carbon element in stainless steel on the metallographic structure is mainly reflected in two aspects. On the one hand, it can stabilize the austenite metallographic structure, and the effect of carbon element is very large, which is about 30 times that of nickel element. There is also another effect. This is because carbon has a very strong affinity with chromium and can easily form a series of complex carbides with chromium. Therefore, the role of carbon in stainless steel is contradictory from the perspective of strength and corrosion resistance.

Understand the law of this effect, you can choose stainless steel with different carbon content according to different use requirements.

For example, the standard chromium content of the five steel grades 0Crl3-4Cr13, which is the most commonly used and most basic stainless steel in the industry, is 12-14%. This is determined after taking into account the factors that cause carbon and chromium to form chromium carbide. , the purpose is to make the chromium content in the solid solution not less than the minimum chromium content of 11.7% after carbon and chromium are combined to form chromium carbide.

As far as these five steel grades are concerned, because of the difference in carbon content, the strength and corrosion resistance are also different. The corrosion resistance of 0Cr13 to 2Crl3 steel is better, but the strength is lower than that of 3Crl3 and 4Cr13 stainless steel. Most of them are used for Made into structural parts, the latter two steel grades can obtain more strength because they contain more carbon. They are mostly used to make springs, knives and other parts that require high strength and wear resistance.

For another example, in order to solve the intergranular corrosion problem of 18-8 chromium-nickel stainless steel, the carbon content in the stainless steel can be reduced to less than 0.03%, or elements (titanium or niobium) with greater affinity than chromium and carbon can be added to make it less susceptible to corrosion. Chromium carbide is formed. For example, when high hardness and wear resistance are the main requirements, the carbon content in stainless steel can also be increased appropriately while the chromium content is increased. This will not only meet the requirements of hardness and wear resistance, but also have better Good corrosion resistance. Stainless steel 9Cr18 and 9Cr17MoVCo are used in industry to make bearings, measuring tools and cutting tools. Although the carbon content is as high as 0.85-0.95%, the chromium content in it has also increased accordingly, so it can still be used. Requirements to ensure corrosion resistance.

Generally speaking, the carbon content in the stainless steel materials that can be used in industry now is very small. The carbon content of most stainless steel materials is in the range of 0.1-0.4%, and the carbon content of acid-resistant steel is mostly 0.1-0.2%. Stainless steels with a carbon content above 0.4% make up only a small portion of the total. This is because in most use cases, stainless steel materials are mainly used to resist corrosion.